1. Field of the Invention
This invention relates to a process for converting methanol to olefins or gasoline and, more particularly, the invention is directed to a catalytic process for selectively converting methanol to olefins having at least three carbon atoms per molecule or paraffinic gasoline components.
2. Description of Related Technology
Diminishing supplies of high quality crude oil feedstocks have resulted in investigations of alternative sources of hydrocarbons to be used for conversion to gasoline or as constituents of gasoline. One such alternative has been the use of methanol as a primary fuel additive for gasoline, and as a feedstock for the production of gasoline.
In the past, a typical route for conversion of methanol to gasoline has been through the use of so-called "shape selective" catalysts such as ZSM-5 aluminosilicates and AMS-1B and HAMS-1B borosilicates, which have been shown to have a strong selectivity for high octane gasoline components and additionally are characterized as having a slow deactivation rate via coke formation. The slow rate of coke formation is believed to result from the relatively small diameter of such catalysts' pores, which do not allow sufficient hydrocarbon polymerization to result in a high coking rate.
In the past, catalytic cracking catalysts containing faujasite Y-zeolites have also been investigated as methanol conversion catalysts. As used in the past, such catalysts have lower activity and a faster deactivation rate via coke formation than corresponding shape selective catalysts. Additionally, faujasite Y-zeolites generally gave higher yields of light C.sub.1-C.sub.4 hydrocarbons. As a result, faujasite Y-zeolites have often been overlooked as methanol conversion catalysts.